Stents are used in surgical procedures to repair or support a body lumen. Stents may be balloon expandable or may be self expanding. That is, stents may be formed from a ductile material and be supplied in a contracted or reduced diameter form to enable deployment to a target lumen and then expanded to a larger diameter by the use of a balloon. In another form a stent may be formed from a resilient material and be supplied in a diametrically or radially constrained form for delivery and then expanded when radial constraint is removed. Such stents may be covered or uncovered.
Stents proposed by Gianturco (U.S. Pat. No. 5,035,706) have a closed zig zag configuration comprising struts and bends between the struts. These stents do not have good dimensional stability because when formed into a cylindrical stent, unless constrained, their diameter is not fixed. This means that in some situations, a stent may put more outwardly radial pressure on a vessel than is desirable or it may not be easy to seal a stent graft within such a cylindrical stent.